Study On High Temperature And Thermal Barrier Coatings Produced By Laser Cladding On Lightweight Materials

Titanium and SiC fiber composites are widely applied to the high temperature parts of hypersonic aerospace vehicles for its excellent properties, however, the high temperature parts facing worsing working conditions with the speed rising. To improve the high temperature resistance of titanium and low coefficient of heat transfer of SiC fiber composites, produce ultra high temperature and thermal barrier coatings on titanium and SiC fiber composites will be very valued.In the present study, Nb-Al-Ti high temperature alloy coatings were produced by laser cladding on TC4 substrate. The influence of Ti addition on microstructure and properties on the coating were investigated through X-ray diffraction, scanning electron microscopy, electron probe microanalyzer, Vickers hardness tester, and thermal analyzer. At the same time, (6%?8%Y2O3)-ZrO2 thermal barrier coatings were produced by plasma spray on SiC fiber composites, then laser glazed the coatings by laser cladding. Also the influence of CeO2 addition on morphology and properties on the coating were investigated through X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectrometer, thermal insulation detecting device.Niobium-based alloy has been one of the most potential superalloy to replace Ni-based, Co-based and Al-based intermediate alloy for its high melting point, low density and excellent high-temperature strength. Its oxidation resistance will be improved significantly by adding Ti and Al into the alloy. The experiments showed that with increasing addition of Ti, the microstructure develops from ?-(Nb,Ti)+ISfeAl to ?-(Nb,Ti)+Nb3Al+Nb2Al, the content of ?-(Nb,Ti) dendrite is decreased, and the content of Nb3Al is increased in the beginning and then decreased, however, the content begins to increase when the addition of Ti more than 30.0 at.%, and Nb2Al occurs at the same time, but the growth morphology of Nb3Al shows the Wilcoxon feature with the addition of Ti is 37.0 at.%. With the increase of Ti additions, the hardness of the coatings is gradually increased. The high temperature oxidation resistance of the coating with 23.0 at.%Ti addition is the highest, which results from high fraction of intermetallic compounds and low degree of microsegregation.6%?8%Y2O3/ZrO2 thermal barrier coating has been widely used in aerospace for the low temperature conductivity and high thermal expansion coefficient. It will improve the stability of ZrO2 at higher temperature by adding different additions of CeO2. Results shown that the content of t-ZrO2 is gradually increased, the holes and cracks are decreased with increasing addition of CeO2. After laser glazing, the surface of coating is as-glazed and the grain size of columnar dendrite gradually reduced with increasing addition of CeO2. Also the thermal insulation of coatings with CeO2 additions is better than traditional thermal barrier coatings, and the thermal insulation increased with increasing of CeO2 addition.